The application of paint to vehicle exterior is typically accomplished by robotic automation. In common application, paint applicators apply paint to moving vehicles as they progress through the paint booth. Using the robotic application, the paint layer thickness may vary from location to location on a vehicle and from vehicle to vehicle at the same location, although not as much as in non-automatic paint applications. Because various performance characteristics of the paint system depend on the paint thickness, proposals for measuring the thickness of each paint layer in a complete paint system have been developed. However, additional accuracy in control is desired.